Process for manufacturing a polyester multifilament yarn

ABSTRACT

A polyester multifilament consisting essentially of filament groups (I) and (II). The filament group (I) is composed of a polyester selected from the group consisting of polyethylene terephthalate, polytrimethylene terephthalate and polytetramethylene terephthalate, and/or a blend and/or copolymer comprising at least two members selected from the polyesters. The filament group (II) is composed of a substrate composed of a polyester selected from the group consisting of polyethylene terephthalate, polytrimethylene terephthalate and polytetramethylene terephthalate, and/or a blend and/or a copolymer comprising at least two members selected from the polyesters and at least one polymer selected from the group consisting of styrene type polymers, methacrylate type polymers and acrylate type polymers, which is added to said substrate in an amount of 0.4 to 8% by weight based on the substrate.

BRIEF DESCRIPTION OF THE INVENTION

The present invention relates to a polyester multifilament yarn. Moreparticularly, the present invention relates to a polyester multifilamentyarn comprising a plurality of filaments groups which have such astructural difference that a remarkable difference in the lengths ofconstituent filaments of the filaments groups is generated when themultifilament yarn is subjected to a woolly treatment or a drawingoperation.

BACKGROUND OF THE INVENTION

In natural fibers to be used for clothes, such as wool and silk,variations of the structure and physical properties among individualconstituent fibers are larger than those in synthetic fibers. Such agreat variation is an advantage rather than a disadvantage taking thedemand of clothes into consideration. Namely, woven and knitted fabricsof natural fibers have a higher bulkiness, a softer touch and a higherstiffness than those of synthetic fibers because of such variations.Accordingly, in the field of synthetic fibers, experiments have beenintentionally done to manufacture mixed multifilament yarns by formingvariations, such as differences in the denier and length amongconstituent filaments.

Conventionally in order to obtain such mixed multifilament yarn, thereis ordinarily adopted a method in which at least two kinds ofmultifilament yarns differing in the physical properties such asshrinkage, elongation and elasticity are independently spun and themultifilament yarns are appropriately opened and mixed at the drawingstep, the false-twisting step or other similar steps. This method isadvantageous in that the length difference among constituent filamentscan easily be adjusted by selecting each kind of multifilament yarn.However, when it is intended to obtain a fine-denier yarn having afineness of less than 150 denier, especially less than 75 denier, whichis eagerly desired at present as a material for a high-quality silky orwoolly product, which was described above, it is necessary to spin atleast two kinds of multifilament yarns having a much finer denier andthen mix them. Generally speaking, the productivity is decreased as thedenier of constituent filaments and the total denier is decreased. Inaddition, spinning and mixing steps are more troublesome than a singlespinning step. Therefore, the yarn-manufacturing cost is increased andthe method is not commercially practical.

As means for producing differences of the structures, physicalproperties, fineness and shapes among constituent filaments withoutcausing a substantial increase of the yarn-manufacturing cost, there hasbeen examined a method, wherein filaments are blended while they arebeing spun. For carrying out this method, there are two methods, i.e., amethod using filaments of the same polymer, and a method comprisingsimultaneously spinning a plurality of polymers differing in theirchemical structures, viscosities and the like.

In the former method wherein one polymer, is spun and blended, theextrusion amounts of the polymer are made different among extrusionholes of a spinneret, whereby there is obtained an assembly of filamentsdifferent in the deniers, sectional shapes and physical properties. Inthis method, however, since cooling of thick-denier filaments is delayedas compared with cooling of thin-denier filaments, there is obtained amultifilament yarn comprising a thick-denier component having loworientation and high elongation and a thin-component having highorientation and low elongation. If this multifilament yarn is subjectedto a woolly treatment by utilizing a false twisting device, thethin-denier component is not easily elongated and is subjected to a hightension. As a result, fine-denier filaments gather in the centralportion of the processed yarn. Contrary to this, since the thick-deniercomponent is easily elongated, thick-denier filaments rise in the outerlayer portion. A woven or knitted fabric formed from this yarn comes tohave a hard touch and a weak stiffness. Namely, the knitted or wovenfabric has a touch and feel quite different from those of a silky orwoolly product for which a soft touch and a high stiffness areordinarily required.

For the reasons set forth above, it is considered that the method ofsimultaneously spinning a plurality of polymers is the only one possiblemeans left for attaining the above-mentioned mixed multifilament yarn.However, combinations of ordinary polymers which manifest substantialdifferences of physical properties under the same spinning conditionsare in fact much more limited. Alternatively, use of special polymersinvolves a risk of deteriorating the feel and touch inherent inpolyesters.

SUMMARY OF THE INVENTION

Under such background, the present inventors have done research with aview to developing a multifilament yarn having a soft touch and a goodstiffness without manifestation of the forgoing defects involved in theconventional techniques, and have found that, if a small amount of apolymer obtained from a certain monomer having an unsaturated bond isblended in a polyester, the microstructure and physical properties ofthe polyester are surprisingly changed. Then, the present inventors havenow completed the present invention based on this finding.

More specifically, in accordance with one fundamental aspect of thepresent invention, there is provided a polyester multifilament yarnconsisting essentially of a filament groups (I) and (II). The filamentgroup (I) is composed of a polyester selected from the group consistingof polyethylene terephthalate, polytrimethylene terephthalate andpolytetramethylene terephthalate, and/or a blend and/or copolymercomprising at least two members selected from said polyesters. Thefilament group (II) is composed of a substrate composed of a polyesterselected from the group consisting of polyethylene terephthalate,polytrimethylene terephthalate and polytetramethylene terephthalate,and/or a blend and/or a copolymer comprising at least two membersselected from said polyesters and at least one polymer selected from thegroup consisting of styrene type polymers, methacrylate type polymersand acrylate type polymers, which is added to said substrate in anamount of 0.4 8% by weight based on the substrate.

In accordance with another fundamental aspect of the present invention,there is provided a process for manufacturing a polyester multifilamentyarn, which comprises: melting independently a polyester (I) selectedfrom the group consisting of polyethylene terephthalate,polytrimethylene terephthalate and polytetramethylene terephthalate or apolymer composition comprising at least two members selected from saidpolyesters and a polymer composition (II) comprising a substratecomposed of a polyester selected from the group consisting ofpolyethylene terephthalate, polytrimethylene terephthalate andpolytetramethylene terephthalate or at least two members selected fromsaid polyesters and at least one polymer selected from the groupconsisting of styrene type polymers, methacrylate type polymers andacrylate type polymers, which is added to said substrate in an amount of0.4 to 8% by weight based on said substrate; extruding said polymers (I)and (II) from different extrusion holes without mingling of the polymers(I) and (II); and after cooling, doubling the extrudates withouttwisting and taking up the resulting multifilament yarn.

DETAILED DESCRIPTION OF THE INVENTION

The filament group (I) of the present invention is composed of apolyester (I) selected from the group consisting of polyethyleneterephthalate, polytrimethylene terephthalate and polytetramethyleneterephthalate or a polymer composition (I) comprising at least twomembers selected from said polyesters. The polyester or polymercomposition (I) may contain a delustering, dyeability-improving orantistatic additive in an amount of up to 10% by weight in thecopolymerized or blended state.

The filament group (II) of the present invention is composed of apolymer composition (II) comprising a substrate composed of at least onepolyester selected from polyethylene terephthalate, polytrimethyleneterephthalate and polytetramethylene terephthalate and at least onepolymer selected from the group consisting of styrene type polymers,methacrylate type of polymers and acrylate type polymers, which is addedto the substrate in an amount of 0.4 to 8% by weight based on thesubstrate. The polymer composition (II) may contain a delustering,dyeability-improving or antistatic additive in an amount of up to 10% byweight based on the whole composition (II).

It is important in the present invention that the average breakingelongation of the filament group (II) be larger than the averagebreaking elongation of the filament group (I). To our great surprise, ithas been found that if a linear compound having bulky substituents onthe side chains, such as a styrene type polymer, a methacrylate typepolymer or an acrylate type polymer, is added to a polyester,orientation of the molecular chain of each constituent filament isdrastically reduced, and accordingly, the elongation is remarkablyincreased. The reason has not completely been elucidated, but ispresumed that because of a peculiar chemical structure of the additivepolymer, it may hardly be elongated in the polyester matrix and may bedispersed in the polyester matrix in the form of fine particles having asize smaller than 500 Å. Such fine particles are present amongmicrofibrils of the substrate polyester while functioning as "rolls,"whereby the above-mentioned phenomena of reduction of the orientationand increase of the elongation will probably occur.

As preferred examples of the additive polymer, there can be mentionedpolymers of styrene and styrene derivatives such as α-methylstyrene,p-methoxystyrene, vinyltoluene, chlorostyrene and dichlorostyrene,polymers of methacrylate derivatives such as methyl methacrylate andethyl methacrylate, and polymers of acrylate derivatives such as methylacrylate and ethyl acrylate. From the viewpoint of the cost, polystyreneand poly(methyl methacrylate) are especially preferred.

It is indispensable that the additive polymer should be contained in anamount of 0.4 to 8% by weight based on the substrate polyester in thefilament group (II). When the content of the additive polymer is lowerthan 0.4% by weight, no substantial effect of reducing the orientationor increasing the elongation can be attained. On the other hand, if theadditive polymer is added in an amount exceeding 8% by weight, theadditive polymer causes a defect, and the strength characteristic of thefilament group (II) is reduced, with the result that the ability to bespun and the stability of the process are considerably degraded.Therefore, incorporation of too large an amount of the additive polymeris not preferred.

In the present invention, it is preferred that the average denier of theconstituent filaments in the filament group (I) be not smaller than theaverage denier of the constituent filaments in the filament group (II).In the present invention, since the filament group (I) has higherorientation and lower elongation than the filament group (II) for theabove-explained reason. When a high tension is imposed during thedrawing or processing step, filaments constituting the filament group(I) tend to gather in the core portion of the multifilament yarn.Accordingly, if the denier of constituent filaments in the filamentgroup (I) is smaller than that of constituent filaments in the filamentgroup (II), the stiffness is weakened in a woven or knitted fabricproduced from the resulting multifilament yarn. On the contrary, if thedenier of constituent filaments in the filament group (II) is smallerthan that of constituent filaments in the filament group (I),thick-denier filaments form the central portion of the mulfifilamentyarn, and thin-denier filaments are arranged in the peripheral portion.As a result, the intended characteristics of a spun-like yarn, such as awoolly or a cotton-like yarn, or a silky yarn are obtained.

When a spun-like yarn or a silky yarn is produced, it is indispensablethat thin-denier filaments should surround thick-denier filaments sothat good hand touch is generated by the thin-denier filaments. Fromthis viewpoint, it is preferred that the number of constituent filamentsin the filament group (I) be equal to or less than the number ofconstituent filaments in the filament group (II). Furthermore, it ispreferred that the total denier De(I) of the filament group (I) and thetotal denier De(II) of the filament group (II) satisfy the requirementrepresented by the following formula: ##EQU1##

When the total denier ratio is within the above-described range, anappropriate bulkiness can be manifested. Contrary to this, if the totaldenier ratio is outside the above-described range, no good balance ismaintained between the filament groups (I) and (II), and accordingly,the bulkiness-manifesting force is reduced.

The polyester multifilament yarn of the present invention can bemanufactured by melting independently a polyester composition (I)consisting essentially of at least one polyester selected from the groupconsisting of polyethylene terephthalate, polytrimethylene terephthalateand polytetramethylene terephthalate and a polyester composition (II)consisting essentially of a substrate composed of at least one polyesterselected from the group consisting of polyethylene terephthalate,polytrimethylene terephthalate and polytetramethylene terephthalate andat least one additive polymer selected from the group consisting ofstyrene type polymers, methacrylate type polymers and acrylate typepolymers, which is added to the substrate in an amount of 0.4 to 8% byweight based on the substrate; extruding the melts from differentextrusion holes without mingling thereof; after cooling, doubling theextrudates without twisting and taking-up the resulting multifilamentyarn.

Blending of polyesters or addition of the additive polymer to thesubstrate polyester may be accomplished by optional methods. Forexample, the blending or addition may be performed at the polymerizationstep, or there may be adopted a method in which the polymers aresimultaneously molten and mixed, cooled and formed into chips.Furthermore, there may be adopted a method in which the polymers aremixed in the form of chips and the mixture is melt-spun. For theblending or addition, in order to enhance the degree of kneading, it ispreferred that a screw type melt extruder be used.

In the present invention, the polymer compositions (I) and (II) may beextruded from different spinnerets, respectively. However, in order toenhance the blend property during a spinning step, it is preferred thatthe polymer compositions (I) and (II) be extruded from differentextrusion holes of one single spinneret. In this case, it is preferredthat the polymer composition (II) be extruded from extrusion holesarranged in the peripheral portion, and the polymer composition (I) beextruded from extrusion holes arranged in the central portion. Thereasons are as follows. First, this arrangement of the extrusion holescontributes to the above-explained multifilament structure which ispreferable for a spun-like yarn or a silky yarn and in which thin-denierfilaments surround thick-denier filaments. Second, the polymercomposition (II) which is only slightly oriented can be extruded fromextrusion holes arranged in the peripheral portion, and therefore, theorientation of the polymer composition (II) is prevented. Third, becauseof this arrangement, polymer flow passages in a spinning pack does notbecome complicated.

In obtaining the polyester multifilament yarn of the present invention,it is preferable that the spun multifilament yarn be taken up at a speedof at least 2000 m/min. When the spinning take-up speed is too low, nosubstantial orientation takes place in the filament group (II), andaccordingly, the styrene type, methacrylate type or acrylate typepolymer added therein fails to function sufficiently as "rolls"described above for preventing orientation of the molecular chain of thepolyester. Accordingly, the effects of reducing the orientation andenhancing the elongation in the filament group (II) over the filamentgroup (I) become insufficient.

In order to enhance the blending characteristic in the polyestermultifilament yarn of the present invention, it is preferred that thepolymer compositions (I) and (II) be extruded from different extrusionholes, cooled and then blended, and the resulting multifilament yarn beinterlaced so that constituent filaments therein be intermingled witheach other by means of a compressed air stream fed through aninterlacing nozzle. When the interlaced multifilament yarn iscontinuously or discontinuously subjected to a drawing step or a drawtexturing step, filaments belonging to the polymer composition (I)locates the central portion of the multifilament yarn forming a coreportion, and filaments belonging to the polymer composition (II) wrapstherearound forming a sheath portion, and accordingly, a splendedspun-like yarn can be produced as disclosed in U.S. patent applicationSer. No. 6,219 filed on Jan. 24, 1979 now U.S. Pat. No. 4,307,565.

As will be apparent from the foregoing description, a polyestermultifilament yarn having a high commercial value can be obtained in avery simple manner. Accordingly, the industrial significance of thepresent invention is very great.

The present invention will now be explained in detail with reference tothe following Examples.

In the following Examples, please note that the intrinsic viscositieswere determined at a temperature of 25° C. in O-chloro phenol solutionhaving a concentration of 8% by weight.

EXAMPLES EXAMPLE 1

Polyethylene terephthalate having an intrinsic viscosity of 0.64 andcontaining 0.5% of titanium oxide as a delustering agent was used as thepolymer composition (I), and a composition formed by blending saidpolyester with polymethyl methacrylate (which will be referred to asPMMA hereinafter) (Delpet 80N supplied by Asahi Kasei) at variousblending ratios described in Table 1 in the form of chips was used asthe polymer composition (II).

The respective compositions were melted, compressed and measured in ascrew type melt extruder having a diameter of 25 mm and they were guidedwithout mingling of flow passages of the respective melts. The melt ofthe composition (II) was extruded from 24 circular-shaped extrusionholes (0.2 mm in diameter) arranged in the peripheral portion of onespinneret to form a filament group (II). The melt of the composition (I)was extruded from 8 circular-shaped extrusion holes (0.3 mm in diameter)arranged in the inner portion of the same spinneret to form a filamentgroup (I).

The extruded filaments of the groups (I) and (II) were cooled andsolidified in a lateral-blow type spinning chimney disposed 110 cm belowthe spinneret by blowing air at room temperature at a speed of 12 m/minthrough the filaments. Then filaments were interlaced with each other byan air stream pressure of 1.5 Kg/cm², which was jetted from aninterlacing nozzle mounted 4.5 m below the spinneret.

Finish was, then, applied to the filaments and the filaments were takenup through two godet rollers rotating at various speeds described inTable 1. The average breaking elongations of the filament groups (I) and(II) in the wound multifilament yarns are also described in Table 1.

                                      TABLE 1                                     __________________________________________________________________________            Filament Group (I)                                                                      Filament Group (II)                                            Spinning  Breaking                                                                           Blending   Breaking                                         Run                                                                              Speed     Elonga-                                                                            Ratio (%)  Elonga-                                          No.                                                                              (m/min)                                                                            de/fil                                                                             tion (%)                                                                           of PMMA                                                                             de/fil                                                                             tion (%)                                                                           Remarks                                     __________________________________________________________________________    1  1000 200/8                                                                              490  0     186/24                                                                             470  comparison                                  2  1000 200/8                                                                              490  2     186/24                                                                             600  embodiment of the                                                             present invention                           3  2000 140/8                                                                              280  0     130/24                                                                             270  comparison                                  4  2000 140/8                                                                              280  1     130/24                                                                             360  embodiment of the                                                             present invention                           5  2000 140/8                                                                              280  2     130/24                                                                             440  embodiment of the                                                             present invention                           6  3000 72/8 170  0     68/24                                                                              140  comparison                                  7  3000 72/8 170  0.2   68/24                                                                              165  comparison                                  8  3000 72/8 170  0.6   68/24                                                                              260  embodiment of the                                                             present invention                           9  3000 72/8 170  1     68/24                                                                              300  embodiment of the                                                             present invention                           10 3000 72/8 170  2     68/24                                                                              365  embodiment of the                                                             present invention                           11 3000 72/8 170  3     68/24                                                                              390  embodiment of the                                                             present invention                           12 3000 72/8 170  5     68/24                                                                              450  embodiment of the                                                             present invention                           13 3000 72/8 170  7     68/24                                                                              480  embodiment of the                                                             present invention                           14 3000 72/8 170  9     68/24                                                                              270  comparison                                  __________________________________________________________________________

In Runs Nos. 1, 3, 6 and 7, since PMMA was not blended or the blendedamount of PMMA was too small, the breaking elongation of the filamentgroup (II) was lower than the breaking elongation of the filament group(I). In Run No. 14, since the amount blended of PMMA was too large, thespinning condition was drastically degraded.

From the results of Runs Nos. 2, 4, 5 and 8 through 13 according to thepresent invention, it will readily be understood that if an appropriateamount of PMMA is blended, the breaking elongation of the filament group(II) can be higher than that of the filament group (I).

EXAMPLE 2

The multifilament yarns obtained in Runs Nos. 6 and 9 through 11 inExample 1 were false-twisted by means of an outer friction type falsetwisting device comprising three shafts, each of which is provided withthree friction discs, at a processing draw ratio of 1.8, a processingspeed of 300 m/min, a heater temperature of 170° C. and friction discperipheral speed of 600 m/min. In case of the multifilament yarnobtained in Run No. 6, filaments of the group (II) gathered in thecentral portion to form a core and filaments of the group (I) werewrapped around the core. In contrast, in case of the multifilament yarnsobtained in Runs Nos. 9 through 11, there were obtained yarns having amulti-layer structure comprising a core composed of the filament group(I) and a wrapper composed of the filament group (II).

Tubular knitted fabrics were produced by means of a circular knittingmachine and by using the thus obtained processed yarns. In case of themultifilament yarn obtained in Run No. 6, the fabric showed a hard touchand a weak stiffness, but in case of the multifilament yarns obtained inRuns Nos. 9 through 11, the fabrics showed a soft touch and a goodstiffness namely a good woolly hand.

EXAMPLE 3

A polymer composition (I) was prepared by blending 70% by weight ofpolyethylene terephthalate having an intrinsic viscosity of 0.64 andcontaining 0.5% of titanium oxide as a delustering agent with 30% byweight of polytetramethylene terephthalate having an intrinsic viscosityof 0.86 in the form of chips. Separately, a polymer composition (II) wasprepared by blending polyethylene terephthalate having an intrinsicviscosity of 0.64 and containing 0.5% of titanium oxide with polystyrene(which will be referred to as PS hereinafter) (Styron 475D supplied byAsahi-Dow) at various blending ratios described in Table 2 in the formof chips.

The compositions were spun and taken up in the same manner as describedin Example 1. The average breaking elongations of the filament groups(I) and (II) in the wound multifilament yarn are described in Table 2.

                  TABLE 2                                                         ______________________________________                                                Filament   Filament Group (II)                                                Group (I)  PS                                                              Spinning         Breaking                                                                             Blending     Breaking                            Run  Speed            Elonga-                                                                              Ratio        Elonga-                             No.  (m/min)  de/fil  tion (%)                                                                             (%)    de/fil                                                                              tion (%)                            ______________________________________                                        1    2000     120/8   235    2      112/24                                                                              330                                 2    2000     120/8   235    4      112/24                                                                              405                                 3    2000     120/8   235    6      112/24                                                                              445                                 4    3800     60/8    79     2       56/24                                                                              136                                 5    3800     60/8    79     4       56/24                                                                              173                                 6    5000     45/8    48     1       42/24                                                                               93                                 7    5000     45/8    48     2       42/24                                                                              128                                 ______________________________________                                    

From the results described in Table 2, it is recognized that in eachRun, the fine-denier filament group (II) had a higher breakingelongation than the thick-denier filament group (I).

EXAMPLE 4

Polytetramethylene terephthalate having an intrinsic viscosity of 0.86and containing 0.5% of titanium oxide was used as the polymercomposition (I). A composition obtained by blending said polyester withpolyethyl acrylate (which will be referred to as PEA hereinafter) in anamount described in Table 3 in the form of chips was used as the polymercomposition (II).

Both the compositions were spun and taken up in the manner as describedin Example 1. The obtained results are described in Table 3.

                                      TABLE 3                                     __________________________________________________________________________            Filament Group (I)                                                                      Filament Group (II)                                            Spinning  Breaking                                                                           Blending   Breaking                                         Run                                                                              Speed     Elonga-                                                                            Ratio (%)  Elonga-                                          No.                                                                              (m/min)                                                                            de/fil                                                                             tion (%)                                                                           of PEA                                                                              de/fil                                                                             tion (%)                                                                           Remarks                                     __________________________________________________________________________    1  1000 150/8                                                                              280  0     140/24                                                                             240  comparison                                  2  1000 150/8                                                                              280  0.5   140/24                                                                             300  embodiment of the                                                             present invention                           3  1000 150/8                                                                              280  1     140/24                                                                             370  embodiment of the                                                             present invention                           4  1000 150/8                                                                              280  2     140/24                                                                             460  embodiment of the                                                             present invention                           5  2000 72/8 180  0     68/24                                                                              140  comparison                                  6  2000 72/8 180  1     68/24                                                                              225  embodiment of the                                                             present invention                           7  2000 72/8 180  2     68/24                                                                              293  embodiment of the                                                             present invention                           8  3000 63/8  91  0     58/24                                                                               82  comparison                                  9  3000 63/8  91  1     58/24                                                                              138  embodiment of the                                                             present invention                           10 3000 63/8  91  2     58/24                                                                              197  embodiment of the                                                             present invention                           __________________________________________________________________________

From the results described in Table 3, it is observed that in each ofsamples obtained in Runs Nos. 2 through 4, 6, 7, 9 and 10, the breakingelongation of fine-denier filaments of the group (II) was higher thanthat of thick-denier filaments of the group (I).

We claim:
 1. A process for manufacturing a polyester multifilament yarn,which comprises: melting independently (I) a polyester selected from thegroup consisting of polyethylene terephthalate, polytrimethyleneterephthalate and polytetramethylene terephthalate or a polymercomposition comprising at least two members selected from saidpolyesters and (II) a polymer composition comprising a substratecomposed of a polyester selected from the group consisting ofpolyethylene terephthalate, polytrimethylene terephthalate andpolytetramethylene terephthalate or at least two members selected fromsaid polyesters and at least one polymer selected from the groupconsisting of thermoplastic styrenic polymers, methacrylic polymers andacrylic polymers, which is added to said substrate in an amount of 0.4to 8% by weight based on said substrate; extruding said polymers (I) and(II) from different extrusion holes without mingling of the polymers toform filaments of polymers (I) and (II) wherein the average denier offilaments of polymer (I) is at least as large as the average denier ofthe filaments of polymer (II); and after cooling, doubling theextrudates without twisting and taking-up the resulting multifilamentyarn.
 2. A process for manufacturing a polyester multifilament yarn asset forth in claim 1, wherein the take-up speed is at least 2000 m/min.3. A process for manufacturing a polyester multifilament yarn as setforth in claim 1 or 2, wherein the polyester of polymer composition (II)is extruded from extrusion holes arranged in the peripheral portion of aspinneret and the polymer composition (I) is extruded from extrusionholes arranged in the inner portion of said spinneret.
 4. A process formanufacturing a polyester multifilament yarn as set forth in claim 1,wherein the multifilament yarn formed by doubling the extrudates issubjected to an interlacing treatment.